The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Laser welding is commonly used to join plastic or resinous parts, such as thermoplastic parts, at a welding zone. An example of such use of lasers can be found in U.S. Pat. No. 4,636,609, which is expressly incorporated herein by reference.
As is well known, lasers provide a semi-focused beam of electromagnetic radiation at a specified frequency (i.e., coherent monochromatic radiation. There are a number of types of radiant sources available; however, infrared lasers or non-coherent sources provide a relatively economical source of radiative energy for use in heating a welding zone. One particular example of infrared welding is known as Through-Transmission Infrared (TTIr) Welding. TTIr welding employs an infrared laser capable of producing infrared radiation that is directed by lenses, diffractive optics, fiber optics, waveguides, lightpipes or lightguides through a first plastic part and into a second plastic part. This first plastic part is often referred to as the transmissive piece, since it generally permits the laser beam from the laser to pass therethrough. However, the second plastic part is often referred to as absorptive piece, since this piece generally absorbs the radiative energy of the laser beam to produce heat in the welding zone. This heat in the welding zone causes the transmissive piece and the absorptive piece to be melted and, with intimate contact, welded together.
However, in the case of those TTIr welding systems that employ a lightguide or lightpipe, the infrared laser light that exits the lightguide or lightpipe is often outwardly dispersed in a fan or cone shape as it passes through the transmissive piece. This dispersion of light may lead to oversized welding zones. That is, as the light exits the lightpipe or lightguide, the light fans outwardly and impacts a larger area of the absorptive piece and transmissive piece interface. This larger area is consequently heated causing a larger welding zone.
Accordingly, there exists a need in the relevant art to provide an apparatus for use with a lightpipe or lightguide that is capable of minimizing the size of a weld zone. Furthermore, there exists a need in the relevant art to provide an apparatus for use with a lightpipe or lightguide that is capable of focusing the laser light to a narrower area that could not otherwise be obtained simply with a conventional lightpipe or lightguide. Lastly, there exists a need in the relevant art to provide a lightpipe or lightguide with an optical horn capable of overcoming the disadvantages of the prior art.